In general, a power window system mounted on a vehicle may have a switch and a driving motor. The power window system may control the driving motor to raise or lower a window glass of the vehicle based on the operation of the switch by the driver. Thus, the driver may easily open and close the window glass of the vehicle to a desired position by only a simple operation of the switch.
Meanwhile, when the driver closes a window glass by a back seat using the switch in the vehicle, an accident may occur. For example, a body portion, such as a finger, an arm, a head, or a neck of a person in the back seat or an object may be caught between the window glass and a doorframe of the vehicle.
As such, a power window system may have a safety function. A safety function has been developed to automatically stop raising the window glass, or to automatically inversely lower the window glass, if an obstacle is detected while the window glass is being raised to protect the obstacle.
Such a power window system may have a ring magnet fixed to a rotating shaft of a driving motor and may have two hall sensors. The two hall sensors may have a phase difference of 90 degrees from each other around the periphery of the ring magnet. The power window system may determine a speed (raising speed), a location (raised or lowered height position), and a direction (raising or lowering direction) of a window glass based on two pulse signals detected by the two hall sensors and may perform the safety function.
In this case, if a fault occurs in one of the two hall sensors, since the power window system may fail to detect a movement direction of the window glass because only one pulse signal is generated, it may fail to perform the safety function. The conventional power window system may fail to cope with these conditions.
In other words, if a fault occurs in one of the two hall sensors, the conventional power window system may detect a speed of the window glass based on one pulse signal generated by the one hall sensor, but may fail to detect a location and a direction of the window glass. As a result, the conventional power window system may fail to perform the safety function.